Power transmission



y 5, 1950 H. F. VICKERS ETAL 2,515,662

POWER TRANSMISSION Filed June 10, 1946 r50 I42 L36 HTTUFNE') PatentedJuly 25, 1950 2,516,862 rowan 'rnausmssrou Harry F. Vickers, Detroit,Kenneth R. Herman, Franklin, and Walter M. Pohl, Birmingham, Mich,assignors to Vickcrs: Incorporated, Detroit, Mich, a corporation prMichigan Application June 10, 1946, Serial No. 675,885

This invention relates to power transmissions, particularly to those ofthetype comprising two or more fluid pressure energy translatingdevices, one of which may function as a pump and another as a fluidmotor.

The invention is more particularly concerned with a hydraulic power andcontrol system adapted for use on vehicles and especially to suchvehicles as switching and mine locomotives having an internal combustionengine prime mover. There have been many proposals and attempts toprovide motor vehicles of this class with infinitely variable hydraulictransmissions and with various automatic and semi-automatic systems forcontrolling the speed ratio to meet the wide 'variety of operatingconditions encountered.

It is an object of the present invention to provide an improved powerand control system which requires an absolute minimum of skill on thepart of the operator and which may be manually set to produceautomatically any desired vehicle speed and vehicle acceleration.

Another object is to provide in a system of this character automaticsupervisory controls which do not normally affect the operation of themanual controls but which when certain operating limits are exceeded,for example, the power capacity of the prime mover or the tractivecapacity of the vehicle wheels will take over control of thetransmission to maintain its output below selected limits.

Another object is to provide in a system of this character a speedregulating control which is free from hunting and which is compensatedto correct for changes in prime mover speed and loads.

It is also an object of the present invention to provide a system havingan improved means of enabling the vehicle to freewheel in eitherdirection in addition to providing an open by-pass across the maincircuit when the controls are in neutral position.

Figure 1 is a diagrammatic view of a power 8 Claims. (Cl. 105-64)transmission and control system embodying a 8 to actuate the usual fuelcontrol by a lever I4.

vided with slidabie control rods 38 and 38 mounted The governed speed ofthe engine may be manually adjusted by any suitable controller such asthe hand lever l5 adjusting the spring ll acting on the lever I4. Theengine It has its output shaft l6 connected to drive a reversiblevariable displacement pump l8 having a yoke 20 which may be angularlyadjusted to vary the direction and volumetric rate of fluid delivery bythe pump. The pump it! is connected by main fluid circuit conduits 22and 24 to a variable displacement fluid motor 26. The latter may beprovided with a swinging yoke 28 which may be angularly adjusted tochange its displacement per revolution over a substantial range, forexample, two to one, without, however, reversing the relation betweenfluid flow and shaft rotation. The output shaft 30 may be connected bysuitable gearing 32 to the driving wheel or wheels 34 of the vehicle.

The pump and motor yokes 20 and 28 are proin bearings 40 and connectedto the yokes by links 42. The control rods 36 and 38 may be actuated incorrelated relation by any suitable means, that illustrated comprising ahorizontally shiftable cam having slots 46 and 48 adapted to coact withfollowers ill and 52 carried by the ends of the control rods. The camslots are so arranged that, when the cam 44 is in the neutral positionillustrated, yoke 20 is maintained in neutral position and yoke 28 inits maximum displacement position. Upon displacement of cam 44 to theleft or right, yoke 20 is first shifted gradually downwardly or upwardlyto its maximum displacement position while yoke 28 remains unchanged.Further movement of the cam 44 holds the yoke 20 in position and swingsthe yoke 28 toward a position of reduced displacement. The

cam 44 thu constitutes a single member for varying the speed ratio andthe direction of power transmission between the pump and motor. Thecam'44 is adapted to be positioned by a hydraulic actuator 54 comprisinga piston slidable within a cylinder 56 and normally biased to centerposition by high rate springs 58 and 60. Thus, whenever fluid underpressure is admitted to one end of the cylinder 58, the spring in theopposite end will be compressed to a degree depending is provided apilot hydraulic system comprising 7 a fluid displacement pump n drivenfrom the engine I and having a suction conduit 84 conncctedto a fluidreservoir 88. The delivery conduit 08, provided with the usual reliefvalve I0 and relief conduit "I2, has an adjustable compensated flowcontrol valve I4 therein and leads to the'inlet port of a four-wayreverse valve I5. The valve I4 is preferably of the type which maintainsany desired flow rate independently of the pressure conditions, the ratebeing adjustable by a dial I5. The return line I8 fromthe reverse valveI0 leads through a pressure responsive backpressure valve 80 to the tank88. The valve I8 is connected to the actuator 54 by conduits 82 and 84.Connected to the delivery line 58 by a branch conduit 85 is a bleedvalve 88 which when open by-passes the delivery of pump 52 back to thetank 55. The valve 88, while not responsive to operating pressure inconduit 58 because it is hydraulically balanced, is neverthelessarranged to be variably opened and closed to regulate that pressure bythe action of certain automatic and manual control means later to bedescribed.

The conduits 82 and 84 for the actuator 54 extend upwardly beyond thevalve I where they are connected in parallel with a closed loop circuit8852 having a pair of fluid pumps 94 and 88 connected in series therein.The pump 84 is driven from the driving wheel 84 by suitable gearing 88while the pump 85 is driven from a free rolling idler wheel I00 bysuitable gearing I02. lIhe pumps 84 and 85 are of equal displacement anddriven at the same speed from their respective wheels so that, if thedriving wheel 84 maintains rolling traction contact without slipping,fluid will be circulated idly through the loop circuit 50-82 with noflow taking place into or out of the conduits 82 and 84.

The control of the bleed valve 88 is primarily in response to vehiclespeed and for this purpose a speed governor I04 may be driven from theidler wheel I00 by gearing I88 and shaft I08. The governor I04 adjuststhe valve 88 through the medium of a T-shaped lever IIO fulcrumed at IIIand is so arranged that an increase in speed tends to open the valve 88and vice versa. The governor I04 is subject to manual adjustment of itsresponsive speed and for this purpose its lower end is arranged to beslid upwardly and downwardlv on the shaft I08 under the control of alever II4 having an adjustable fulcrum H8 and a control rod II8 which ismanually operated by a cam I20. When the cam I20 is in its neutralposition slightly clockwise from the position shown, the rod H8 is atits lowest position in which the speed governor I04 holds the valve 88open at zero speed. Rotation of the cam I20 to either side ofits neutralposition progressively raises the rod I8 through the action of the camslot I22.

The cam I20 has a second cam slot I24 having pending upon the directionof movement of cam I20. The cam I20 is provided with a handle I84 bywhich the cam may be rotated about its axis. The handle I85 is pivotedon a transverse axis I38 for movement toward and away from the plane ofthe drawing and has an upward extension I40 which projects through astationary plate I42.

The plate I42 (see Figure 2) is provided with a zig-zag slot I44 with acentral vertical portion I45 through which the handle extension may bemoved laterally when in neutral position. The plate I42 is provided witha bore I48 intersecting the portion I48 and a pin I50 is slidablc in thebore t selectively block movement of the handle extension I40 from oneside to the other of neutral position. Pin I50 is controlled by governorI04 by the extension I52 of lever III, link I54 and bellcrank I55.

For the purpose of supervising the operation of lever I35 to prevent thepower capacity of engine I0 from being exceeded, there is provided ahorsepower limiter comprising a cylinder I58 having a spring-loadedpiston I50 therein, the rod I52 of which carries a hyperbolic cam I54.In the spring retracted position of piston I50, the cam I54 permits freerotation of cam I20 through its full stroke in either direction. Whenthe cam I54 is projected to the left it coacts with a pin I55 carried bycam I20 to limit the possible angular movement of cam I20. The curvatureof cam I54 is such that the farther the cam is projected to the left,the smaller is the possible are of movementof cam I20, the relationshipbetween th two preferably being a hyperbolic function. The cylinder I58is connected to the main circult lines by a conduit I58 which connectswith lines'22 and 24 through check valves I10 and I12, respectively.Thus the line I58 receives fluid from whichever one of the main circuitlines happens to be at the higher pressure at any given moment and thepiston I50 moves to the left in proportion to the fluid pressure in lineI58.

For the purpose of providing a positive neutral and also a free-wheelingaction there is provided a neutral by-pass and free-wheeling controlwhich may be actuated from the cam I20 by rod I25. For this purpose, alever H4 is fulcrumed at I15 to operate the spool of a four-way reversevalve "8. The latter is connected across the main circuit lines 22 and24 by branch conduits I and I82 and the internal porting and lands ofthe spool are so proportioned that when in central position, the branchconduits I80 and I82 are open to each other. In the body of the valve H8is a check valve I84, the inlet I85 of which is adapted to beselectively connected with conduit I80 or I82 depending upon which ofthe two extreme positions the spool of valve Ill occupies.

The adjustable fulcrum H5 of the lever H4 is adapted to be controlled inresponse to the speed and load conditions at the prime mover I0. Forthis purpose, fulcrum H5 is connected a steep rise portion adjacent theneutral posi- I tion and with circular dwell portions for a considerableare either side thereof. Cam slot I24 controls a rod I25 horizontallyshiftable in bearings I28 and connected by bellcranks I80 and I32 andlink I84 to the shiftable spool of reverse valve I8. The action is suchthat on slight movement from neutral position of cam I20, the valve I8is shifted to either of its extreme positions deby a link I88 to afloating lever I90. The left end of the lever I90 is operated by a camI02 pivoted at I94 and actuated from the speed regulator I2 by a linkI85 and bellcrank I88. The righthand end of lever I80 is operated from aspring-loaded piston 200 slidable in a cylinder 202, the upper end ofwhich is connected to the intake manifoldof the engine through a conduit204. The piston 200 is connected to lever I 80 by a lost motionconnection comprising a dashpot piston 20s slidable m a cylinder 208which is pivotally attached to the lever I. A centering spring 2" servesto normally maintain the righthand end of lever I90 in a centeredposition but permits the same to move upwardly or downwardly when thereis a change in the position of piston 200 more rapid than the dashpotwill accommodate without yielding.

I In operation, with the engine I running and with the speed adjustmentlever I36 moved from neutral to the position shown on the drawing, thismovement will have positioned the valves I6 and I18 to the'left andright, respectively, as

shown, this action having been caused by the cam slot I24 acting throughthe rod I26 and linkages I38, I82, I34 and H4. The remaining parts onthe drawing are shown in the positions they would occupy for an instantafter. lever I36 is shifted and before the automatic controls havecaused the vehicle to start in motion. Movement of the cam I20 alsoshifted the speed governor I04 bodily upward on shaft I08 and throughlever IIO closed the bleed valve 88. This causes the entire quantity offluid passed by flow control valve I4 to be delivered from pump 62 intothe righthand end of cylinder 56 through passage 68, valve I6 andpassage 82. Piston 54 is accordingly shifted to the left and the cam 44,through the action of slot 46, moves the yoke 20 downwardly causing thedelivery of pump I8 to increase proportionately. Oil is accordinglypumped from conduit 24 into conduit 22 which drives the fluid motor 28in a direction which for the present purposes will be termed forward.

The speed of movement of piston 54 and cam 44 is determined by theadjustment of the flow regulating valve I4 and can be set to give anydesired vehicle acceleration rate. As soon as the vehicle comes up to aspeed corresponding to the setting of lever I36, the governor I04 willhave pulled the lever IIO downwardly to partially open the bleed valve88. When it has opened to the degree where the value of pressure inconduits 82, 68 and 86 will force the same quantity of oil through valve88 as passes through valve 14, the piston 54 will stop moving and holdthe cam 44 and yokes 20 and 28 in that adjusted position.' The pressuremaintained in conduits 82, 66 and 86 will depend, of course, upon theposition of piston 54 and compression of the spring 58. It will be seenthat the action is such as to automaticalLv maintain the vehicle speedat a constant value since any increase above that value will tend toopen valve 88 farther, thus permitting more oil to bleed out of line 68than comes into it through the flow control I4 which will permit thepiston 54. to move back slightly to the right and correspondingly reducethe displacement of pump I6 and speed of the vehicle. The oppositeaction wilt occur upon a decrease in speed.

The speed regulating action of governor I04 is further compensated forload variations as reflected at the engine I0. Assuming that the vehiclemeets increased load resistance, as, for example, by entering anupgrade, then the subatmospheric pressure in the engine manifold willrise permitting the spring pressed piston 200 to move downwardly. If therate of movement is sufliciently rapid, the dash-pot piston 206 willcarry the cylinder 208 with it overcoming the action of centering spring2I0 and shifting the righthand end of lever I90 downwardly which actsupon the adjustable fulcrum I I6 to shift the lower end of speedgovernor I04 also downwardly thus tending to open the bleed valve 88 andpermit piston 54 to shift back toward center. This temporariLv reducesthe speed ratio of the transmission I6 and 26, or, to put it anotherway, increases the mechanical advantage of the engine over the drivingwheels and makes it possible for the engine I0 to more quickly pick upthe additional load and come to a steady state without hunting of thespeed governor I2. The centering spring 2 II will in a small timeinterval restore the lever I 60 to its centered position regardless ofthe position of piston 200, and the action just described is only atransitory condition occurring when there are rather rapid load changes.

Since the heavier load requires a larger opening of the fuel regulatorI4, the speed governor I2 will govern the engine to a slightly lowerspeed. However, this eflfect would cause thewehicle to operate atacorrespondingly reduced speed if the ratio of transmission remains thesame as before. In order to compensate for this characteristic of theengine governor I2, the cam I82 will take up a new position clockwisefrom the position illustrated which in turn will raise the left end oflever I and the lower end of speed regulator I84. This has the effect ofslightly closing the bleed valve 88 and causing the piston 64 to take upa new stable position slightly to the left of that occupied before theadditional load was imposed. In this way, the speed of the vehicle ismaintained at the same value regardless of load.

In the event that the setting of the flow regulator valve oracceleration control I4 should be too high for a slippery trackcondition, the supervisory control originating at pumps 94 and 86 willbe brought into play. Thus, when the driving wheel 34 starts to slip, itwill cause pump 84 to deliver oil into conduit 90 faster than pump 96withdraws it therefrom and the difference will be delivered into conduit84. Likewise, the deflciency in conduit 32 between the output of pump 86and the intake of pump 94 will bedelivered into conduit 92 throughconduit 82. This counteracts the effect of the oil delivered from pump62 through conduits 68 and 82 and retards the rate of acceleration ofthe vehicle or may even stop it completely by holding the piston 54stationary. Thus accelerations of the driving wheel 34 are held down toa point where it cannot rotate ahead of the idler wheel I00 even thoughthe controls be manually set for a higher rate of acceleration.

In the event that the acceleration rate set by the manual controls wouldexceed the power capacity of the prime mover I0, the horsepower limitingpiston I60 comes into play and limits the maximum setting which can begiven to the speed lever I36. This control also comes into play underconditions where the vehicle is operating at high speed under medium orlight load and the load increases beyond the power capacity in theengine I0. In such event, the pressure from the main circuit line 22 inforward drive will be transmitted through check valve I10 and line I68to the piston I60 and will positively force the cam I20 clockwise by theamount necessary to keep the horsepower requirement within thecapabilities of engine I0. Similar action occurs also when the vehicleis operating in reverse.

It will be noted that the system provides control of acceleration ratesby the mechanism above described and that it is ineffective to controldeceleration. The latter type of control is unnecessary in view of thefact that the free wheeling check valve I84 is provided. Thus, in theevent that the speed lever I36 should be suddenly shifted from a highspeed setting to a neutral position, the system would not be overloadedin any way because the inertia of the vehicle will continue the motor 26in operation as a pump. The excess fluid delivered into line 24 beyondthat accepted therefrom by the pump I8 will pass through the branch I82,valve I18, check valve I84 and branch I80 back to the forward deliveryline 22.

When the control lever I36 is set for reverse operation, valves I6 andI18 are shifted to their opposite position from those shown on thedrawing. This has the effect of transferring delivery of pump 62 to theconduit 84 and left end of cylinder 56, thus producing the same type ofcontrol as previously described except that cam 44 is shifted to theright and cam slot 4c will raise the yoke 20 rather than lower it. This,of course, reverses the delivery condition in the main circuit 22-24 andcauses the motor 28 to operate in the opposite direction. The shiftingof valve I18 also transposes connection of check valve I84 with thebranch conduits I80 and I82 so that it then becomes effective to blockflow from conduit 24 to conduit 22 and permits free flow in the oppositedirection.

While the check valve I84 prevents overloading of the mechanism in theevent of sudden shifting of speed lever I36 from a high speed to aneutral position, it would be possible to dangerously overload theequipment with the controls thus far described if the lever weresuddenly moved from high speed forward to high speed reverse forexample. That is because the valve I18 reverses the connections of checkvalve I84 as the lever is moved through neutral which would have theeffect of suddenly blocking the outlet path for the oil delivered bymotor 26 (acting as a pump) into conduit 24.- In order to prevent this,the neutral interlock pin I56 is held in the position shown in Figure 2at all times when the vehicle speed is above a predetermined value.Thus, the extension I46 of the lever I36 is confined either to the upperportion of slot I44 (as shown in Figure 2) during forward operation orto the lower portion thereof during reverse operation. When the speeddrops to a safe small value, the pin I50 becomes fully retracted, thuspermitting transfer from the upper to the lower slot portion or viceversa. Preferably the speed at which pin I58 is fully retracted is suchthat it is possible to rapidly .rock the vehicle forward and back wheresuch action is desirable under bad traction condition.

In the form illustrated, the invention includes means for controllingnot merely the displacement of the pump I8 but also that of the fluidmotor 26. This has the eifect of greatly increasingthe range of speedratios available with a given size of pump and motor combination since,when the full displacement of the pump I8 is reached, further increasesin speed may be obtained by decreasing the displacement of the motor 26.This contributes materially to the economy of construction since smallerhydraulic units may be utilized.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. A hydraulic drive and control system for a motor vehicle or the likecomprising a pump and a fluid motor connected together in a main powercircuit, means for adjusting the relative displacements of the pump andmotor to vary the ratio of power transmission between them, meansresponsive to vehicle speed for operating the displacement adjustingmeans, manual means for changing the setting of the speed responsivemeans, and adjustable means for controlling the rate of change ofrelative displacement independently of the speed of manual movement ofsaid manual changing means whereby the rate of acceleration of thevehicle may be controlled.

2. A hydraulic drive and control system for a motor vehicle or the likecomprising a pump and a fluid motor connected together in a main powercircuit, means including a hydraulic actuator for adjusting the relativedisplacements of the pump and motor to vary the ratio of powertransmission between them, means including a valve con trolling saidactuator responsive to vehicle speed for operating the displacementadjusting means, manualmeans for changing the setting of the speedresponsive means, and adjustable means including a flow regulating valvefor controlling the rate of change of relative displacementindependently of the speed of manual movement of said manual changingmeans whereby the rate of acceleration of the vehicle may be controlled.

3. A hydraulic drive and control system for a motor vehicle or the likecomprising a pump and a fluid motor connected together in a main powercircuit, means for adjusting the relative displacements of the pump andmotor to vary the ratio of power transmission between them in eitherdirection, a by-pass valve connected across the main circuit andoperated by said means to bypass the pump when said means is in neutralposition, and a check valve also connected across the main circuit forpermitting the fluid motor to overrun the pump, said by-pass valvehaving means for reversing the connection of the check valve withrespect to the main circuit when said means is moved to reverse thedirection of the transmis- 4. A hydraulic drive and control system for amotor vehicle or the like having an internal combustion engine andcomprising a pump and a fluid motor connected together in a main powercircuit, means for adjusting the relative displacements of the pump andmotor to vary the ratio of power transmission between them, meansresponsive to vehicle speed for operating the displacement adjustingmeans, manual means for changing the setting of the speed responsivemeans, and means responsive to engine speed changes for adjusting thevehicle speed respon sive means.

5. A hydraulic drive and control system fora motor vehicle or the likehaving an internal combustion engine and comprising a pump and -a fluidmotor connected together in a main power circuit, means for adjustingthe relative displacements of the pump and motor to vary the ratio ofpower transmission between them, means responsive to vehicle speed foroperating the displacement adjusting means, manual means for changingthe setting of the speed responsive means, and means responsive toengine load changes for adjusting the vehicle speed responsive means.

6. A hydraulic drive and control system for a motor vehicle or the likehaving an internal combustion engine and comprising a pump and a fluidmotor connected together in a main power circuit, means for adjustingthe relative displacements of the pump and motor to vary the ratio ofpower transmission between them, means responsive to vehicle speed foroperating the displacement adjusting means, manual means for changingthe setting of the speed responsive means, and means responsive toengine load and speed changes for adjusting the vehicle speed responsivemeans.

7. A hydraulic drive and control system for a motor vehicle or the likecomprising a pump and a fluid motor connected together in a main powercircuit, means for adjusting the relative displacements of the pump andmotor to vary the ratio of power transmission between them, meansresponsive to vehicle speed for operating the displacement adjustingmeans, manual means for changing the setting of the speed responsivemeans, and means eflective to reduce the speed setting of said manualmeans whenever the horse-power transmitted by the transmission exceeds apredetermined maximum.

8. A hydraulic drive and control system for a motor vehicle or the likehaving a driven traction wheel and a free-rolling idler wheel comprisinga pump and a fluid motor connected together in a main power circuit,means for adjusting the relative displacements of the pump and motor tovary the ratio of power transmission between them, means including apump, a fluid actuator and a control valve responsive to vehicle speedfor operating the displacement adjusting means, manual means forchanging the setting of the speed responsive means, and means includinga pair of pumps hydraulically connected in series andconnected inparallel with said actuator, one connected to each wheel, and responsiveto a difference between the speeds of said wheels for limiting theacceleration imparted to the vehicle by operation of the manual means.

HARRY' F. VICKERS. KENNETH R. HERMAN. WALTER, M. POHL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

